The present invention relates to a lamp ribbon, i.e. to a flexible belt shaped cable construction bearing a series of bulbs which are energized by electricity passing through electrical conductors incorporated in said belt construction so as to be illuminated. Such a lamp ribbon is typically used for decorative purposes, such as for instance for decorating a place of business or a showcase therein, or for embellishing a display in a shop window, and can be either extended straight or wound or draped or festooned in any of a variety of configurations about or from various objects, presenting when energized an attractive appearance of a sequence of glowing points of light.
In FIGS. 1 and 2 of the accompanying drawings there is shown the construction of a conventional such lamp ribbon: FIG. 1 is a perspective drawing showing the belt construction and one of the plurality of lamps mounted thereon, and FIG. 2 shows a cross section of said one of the plurality of lamps and its mounting arrangements, and is taken in a plane shown by the arrows II--II in FIG. 1. The details of this conventional construction will now be explained.
As seen in FIG. 1, the belt construction denoted by the reference numeral 1 comprises an upper belt layer 2 (from the point of view of the figure; in this specification, spatially referent terms should henceforward always be understood as being with reference to the relevant figure, and the "front" or "upper" surface of the lamp ribbon is considered as being that one on which the lamps are mounted, while the "rear" or "lower" surface is considered as being the opposite surface to said front surface) and a lower belt layer 3, both of which are formed from an electrically insulating material which is flexible, such as for instance from a synthetic resin. The upper belt layer 2 and the lower belt layer 3 are sandwiched together on either side of two electrical conductors 4 and 5, which extend in parallel side by side, and which themselves are formed as thin ribbons which are also flexible, being made for example of metal. An incandescent type electric bulb 6 is mounted on the belt construction 1, being supported in a mounting tube 7, and has two terminal wires 8 and 9.
In more detail, as best seen in FIG. 2, the mounting of the electric bulb 6 to the belt construction 1 has in such prior art construction been performed as follows. A short part of the upper belt layer 2 above the two conductors 4 and 5 has been removed, the mounting tube 7 has been fixed to the upper surface of the upper belt layer 2 so as to surround the thus exposed portions of the conductors 4 and 5 by plastic welding under pressure or the like, the two wire terminals 8 and 9 of the electric bulb 6 have been led downwards from the body of said bulb 6 until they meet respectively the conductors 4 and 5, and, by poking the free ends of said two wire terminals 8 and 9 into the belt construction 1 along the upper surfaces of said respective conductors 4 and 5 for a certain distance in the longitudinal direction, these end portions of said two wire terminals 8 and 9 have been made to lie along and in contact with the respective conductors 4 and 5, being squeezed thereagainst by the material of the upper belt layer 2. The reference numeral 45 denotes a layer of adhesive material for securing the lamp ribbon to an object to be decorated, such as for example the edge of a showcase or a wall or ceiling of a shop.
This construction is relatively cheap to produce, but has deficiencies as follows.
First, since the electric bulb 6 is not removable from the belt construction 1, if the electric bulb 6 becomes burnt out or otherwise fails over a period of use, it is impossible to change the electric bulb 6 by itself, and accordingly if the lamp ribbon as a whole is left in service an unsightly gap appears in the sequence of glowing points of light presented thereby, which deteriorates the appearance thereof. On the other hand, changing the entire lamp ribbon because just one of the bulbs thereon has failed is obviously uneconomic, especially if the length of the portion of lamp ribbon used in one piece is quite long.
Next, since in the above described prior art construction the mounting tube 7 which supports the electric bulb 6 is welded by plastic welding to the front surface of the belt construction 1, when this is done the part of said front surface of the belt construction 1 surrounding the base of the mounting tube 7 also becomes melted, which not only is unsightly and deteriorates the appearance of the finished lamp ribbon, but also can cause some permanent or fixed bending of the upper belt layer 2, which can in its turn cause permanent bends to be formed in the finished lamp ribbon, which will mean that its free drapability is affected. In such a case, the appearance of a finished display including the lamp ribbon as an ornament may become rather peculiar, because the lamp ribbon does not flex freely and does not hang straight by the action of gravity, as should be desirable. In short, from this point of view, it is desirable that the flexibility of the finished lamp ribbon product should be uniform throughout, or at least that, where portions of said lamp ribbon are inevitably stiffened due to the presence of the lamp units mounted thereon, these portions of the lamp ribbon should be stiffened straight so as to form straight sections.
Next, in the case that the material of the upper belt layer is transparent, which is typically the case in order to present an interesting appearance, the end portions of the two wire terminals 8 and 9 lying along and in contact with the respective conductors 4 and 5 on the front sides thereof are visible from the front of the lamp ribbon (i.e. from the upper side thereof in FIG. 1), which again is unsightly and deteriorates the appearance of the finished lamp ribbon.
Next, since part of the front or upper belt layer 2 is required to be removed in order to poke the free ends of the two wire terminals 8 and 9 into the belt construction 1 along the upper surfaces of the conductors 4 and 5, this causes a deficiency in electrical insulating characteristics on the front side of the finished lamp ribbon, and thereby a risk is caused of electric shock during use, or of an electrical accident which might for example lead to fire.
Further, because the two wire terminals 8 and 9 are inserted into the belt construction 1 and lie along and against the upper surfaces of said respective conductors 4 and 5 for a certain distance in the longitudinal direction, but are not positively secured or contacted electrically to said conductors 4 and 5, being instead just squeezed thereagainst by the material of the upper belt layer 2, thereby there remains a possibility that poor contact between one of these wire terminals and its conductor may cause one of the bulbs 6 not to be lit when the lamp ribbon is supplied with electrical energy. This will again cause an unsightly gap to appear in the sequence of glowing points of light presented by the lamp ribbon and will deteriorate the appearance thereof.
Yet further, this inserting of the wire terminals into the belt construction 1 along the longitudinal direction thereof is difficult to perform automatically, and as a result this prior art lamp ribbon is expensive to manufacture.
Finally, there is a slight risk that, during the process of poking the free ends of the two wire terminals 8 and 9 into the belt construction 1 along the upper surfaces of the conductors 4 and 5, the scraping of one of the wire terminals along its conductor may break said conductor, which is catastrophic for the performance of the lamp ribbon as a whole, since typically such a lamp ribbon is used by an electrical voltage being applied between one pair of ends only of the conductors 4 and 5. Thus, if one of the conductors should become broken in such a fashion, all the bulbs on the other side of the break point from the electrical source will fail to light, which will render the lamp ribbon as a whole quite unserviceable. Since the conductors 4 and 5 in general are stronger than the wire terminals 8 and 9, the risk of such an occurrence is small; but it is present.
To date no construction for a lamp ribbon has been conceived of that satisfactorily avoids the above mentioned problems.